1. Field of the Invention
The present invention relates to a control system capable of changing the running modes to be used for controlling the output torque of an automatic transmission, in accordance with the road situations of a route to be followed by the vehicle.
2. Related Art
As well known in the art, a stage type automatic transmission is provided with a gear transmission mechanism, frictional engagement units for changing the torque transmission routes of the gear transmission mechanism, and a lockup clutch. In order to control the running performance of the vehicle in accordance with the road situations under which the vehicle is to run, the automatic transmission of this type is preset with a plurality of kinds of running modes including a normal mode, an economy mode, a snow mode, a sport mode and a power mode, which can be changed by the operation of the driver.
On the basis of the running states, as detected during the run of the vehicle, such as the data including the vehicle speed and the throttle opening and the individual running modes (or shift diagrams), moreover, the frictional engagement unit and the lockup clutch are applied/released to control the output torque of the automatic transmission.
However, the running performance of the vehicle depends upon the conditions such as the hill climbing resistance of the road or the frictional resistance of the road to the wheels, and these conditions change moment by moment according to the situations of the road. Merely by changing the running mode by the manual operation of the driver, therefore, an output torque matching the road situations may be achieved to lower the running performance and the drivability.
In recent years, however, the navigation system has been mounted on the ordinary vehicle. This navigation system is constructed to hold maps as electronic data in a recording medium such as CD-ROM and to locate the position of the vehicle by the GPS (Global Positioning System) or the self-contained navigation (or dead reckoning navigation) utilizing artificial satellites so that the present position or moving locus of the vehicle or the route to be followed may be visually outputted to a display unit such as a CRT by combining those data, or so that the running direction may be guided by voices.
The electronic map to be employed in this navigation system can be stored with not only information such as the arrangement of roads, public facilities or rivers but also slopes of roads or legal regulations for road traffic. A variety of information such as the coefficients of friction of road surfaces, as obtained by the actual runs, can be additionally stored. As a result, the information, as obtained by the navigation system, not only guides the vehicle to the destination but also can be used for controlling the engine, the transmission, the brake and the suspension when the vehicle is to run on the route to be followed.
One example of an invention, in which the information obtained by the navigation system is thus applied for controlling the automatic transmission of the vehicle, is disclosed in JP-B-6-58141. The control system for an automatic transmission, as disclosed in the gazette, comprises: memory means (ROM) stored with shift patterns (or shift diagrams) for an economy run or a high output run; running state detecting means for detecting the running state of the vehicle; and control means for controlling the speed change of the automatic transmission on the basis of the shift patterns and the running states. Further comprised are: a navigation system for storing road information for guiding the running of the vehicle; present position detecting means for detecting the present position of the vehicle; and change means for changing the shift pattern to another in accordance with the road information concerning the environment of the present position.
According to the control system for the automatic transmission, this automatic transmission is controlled according to the shift pattern in the selected running mode. When the information of a curve of the road or an unpaved road is detected, the shift pattern is changed to another in accordance with the detected information so that the control of the automatic transmission is executed by the changed shift pattern. As a result, there are achieved the advantage that the shift is inhibited at the time of running on the curve or that the shift is inhibited at the time of running on a low surface friction road such as the unpaved road.
However, the control system for the automatic transmission, as disclosed in the aforementioned gazette, detects the road situations during the run of the vehicle and changes the shift pattern on the basis of the detected road situations. As a result, the running characteristics of the vehicle on the route to be followed to the destination are disadvantageously different from those, as intrinsically intended by the driver, that is, which of the mileage or the driving force is to be stressed. Moreover, the absence of the running mode of the running characteristics matching the situations of the route to be followed may lower the running performance or the drivability at the actual run.